The many problems associated with adhering dentures to gum tissue by means of adhesives has resulted in the development of various retention means based on the use of magnets. Examples of dental appliances of the general type can be found in U.S. Pat. Nos. 4,184,252, 4,209,905, 4,302,189 and 4,431,419; in PCT International Publication WO 82/03547, dated Oct. 28, 1982; and in U.S. Pat. No. 4,626,213 in which one of the present applicants is a named inventor.
In magnetic dental retention appliances of the general character, wherein a denture is retained in place through the interaction of a magnet embedded in the denture and a magnetizable keeper embedded in the patient's mouth, it has been inadvisable to use different metallic materials of construction because of the corrosive galvanic action established between such metals in the presence of the electrolytic medium constituted by the saliva in the mouth. This has deterred the use of some materials of construction in magnetic dental retention appliances, despite the advantages such materials may offer. In general, and as a practical matter, only ferromagnetic materials may safely be employed; the preferred material being ferromagnetic stainless steel.
The inability to use diverse materials is a particularly frustrating obstacle to the use of optimum materials of construction in dental restorations requiring implantation of retention means within the bone structure of the jaw beneath the tissues of the gum and the mucous membrane defining the gingival margin of the gum structure.
While galvanic contact occuring in the electrolytic medium of the saliva in the mouth is referred to in International Publication WO 82/03547, the Publication does not offer a solution to the above discussed deficiencies in prior magnetic dental appliances.